(1) Field of the Invention
This invention relates to a deformation sensitive electroconductive knitted or woven fabric which is changed in electroconductivity at the deformed portion, when a deformation such as stretch or compression is applied.
More specifically, the present invention relates to a deformation sensitive electroconductive knitted or woven fabric which is changed in electroconductivity by one figure or more at the portion deformed by deformation such as stretch or compression as compared with that before deformation, also to a deformation sensitive electroconductive device having electrodes provided on the deformation sensitive electroconductive knitted or woven fabric which can detect the change in electroconductivity which occurs by deformation of said knitted or woven fabric by electrical characteristics such as electrical resistance, and further to a deformation detecting unit having a means for fixing the deformable electroconductive device onto a subject to be tested.
(2) Description of the Prior Art
In the prior art, as the materials which are changed in electrical characteristics such as electrical resistance by compression deformation, there have been known pressure sensitive electroconductive sheets in which electroconductive metal particles, etc. are mixed in a rubber base material such as silicone rubber. These are disclosed in, for example, U.S. Pat. No. 4,138,369 (corresponding Patents: DE No. 2744800, Japanese Laid-open Patent Publication Nos. 43749/1978, 102957/1978) as the material in which electroconductive metal particles and an alkyltitanate compound are mixed in a silicon rubber and in U.S. Pat. No. 4,273,682 (corresponding Patents: DE No. 2757870, Japanese Laid-open Patent Publications Nos. 79937/1978 and 80350/1979) as the material in which electroconductive materials comprising asbestos-like graphite particles of about 40 to 160 .mu.m are mixed.
These elastomer sheets are made to exhibit pressure sensitive electroconductivity by mixing electroconductive fillers such as electroconductive carbon into elastomer sheets.
However, for pressure sensitive electroconductivity to be exhibited, a large amount of electroconductive fillers is required to be mixed, whereby inherent rubber elasticity of an elastomer is markedly damaged and the most important practical characteristic of durability against repeated compression deformation becomes poor. Also, since it is difficult to mix the above electroconductive fillers with good reproducibility, uniformness is poor and therefore reproducibility in electrical resistance change corresponding to compression deformation is inferior. Accordingly, when employed for, for example, a sensor, it is lacking reliability and hence difficulty applicable for uses in which high reliability is demanded.
On the other hand, electroconductive knitted or woven fabrics endowed with electroconductivity by metal plating, etc. have also been known and used in uses such as electromagnetic wave shielding material, electrode plates, etc. These may include, for example, an electroconductive fabric formed by first applying coating of a synthetic resin solution on a fabric to fill up between the crossed portions, carrying out chemical plating and further electroplating thereon to provide a synthetic resin layer thereon with an aim to obtain an electrically conductive fibrous fabric, as disclosed in Japanese Patent Publication No. 27400/1965; a microwave or high frequency shielding material prepared by formation of a metal layer with a thickness of 0.02 to 2 .mu.m on a fibrous sheet such as knitted or woven fabric, as disclosed in U.S. Pat. No. 4,439,768 (corresponding Patents: EP-10712, Japanese Laid-open Patent Publication No. 74200/1980); and a material for uses such as electromagenetic wave shielding, static charge removal and reflection of electrical radiation formed by a metal layer by performing arc flame spray coating on a woven fabric or unwoven fabric, as disclosed in Japanese Laid-open Patent Publication No. 18340/1985.
These electroconductive knitted or woven fabrics have been utilized as materials having electroconductivity or materials for reflecting electrical radiation, and not utilized as the material which is changed in electrical characteristics by compression deformation such as the pressure sensitive elastomer as described above or by stretch deformation as in the present invention.
Thus, there has been no pressure sensitive electroconductive material having high reliability at all, and there is also no pressure sensitive electroconductive material utilizing a knitted or woven fabric.
Further, there has been no technical thought concerning other deformation than compression deformation, for example, the so called stretch sensitive electroconductivity which means change in electroconductivity by stretch deformation, as a matter of course, and there existed no material which can exhibit such stretch sensitive electroconductivity at all.